Physical vapor deposition system and processes

ABSTRACT

A physical vapor deposition (PVD) chamber and a method of operation thereof are disclosed. Chambers and methods are described that provide a chamber comprising an upper shield with two holes that are positioned to permit alternate sputtering from two targets. A process for improving reflectivity from a multilayer stack is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/812,622, filed Mar. 1, 2019, the entire disclosure of which is herebyincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to substrate processingsystems, and more specifically, embodiments pertain to physical vapordeposition systems and processes for physical vapor deposition.

BACKGROUND

Sputtering, alternatively called physical vapor deposition (PVD), isused for the deposition of metals and related materials in thefabrication of semiconductor integrated circuits. Use of sputtering hasbeen extended to depositing metal layers onto the sidewalls of highaspect-ratio holes such as vias or other vertical interconnectstructures, as well as in the manufacture of extreme ultraviolet (EUV)mask blanks. In the manufacture of EUV mask blanks, minimizing particlegeneration is desired, because particles negatively affect theproperties of the final product. Furthermore, in the manufacture of anEUV mask blank, a multilayer reflector comprising alternating layers ofdifferent materials, for example, silicon and molybdenum, is depositedin a PVD chamber. Contamination of the individual silicon and molybdenumlayers caused by cross-contamination of the silicon and molybdenumtargets can be a problem, which leads to EUV mask blank defects.

Plasma sputtering may be accomplished using either DC sputtering or RFsputtering. Plasma sputtering typically includes a magnetron positionedat the back of the sputtering target including at least two magnets ofopposing poles magnetically coupled at their back through a magneticyoke to project a magnetic field into the processing space to increasethe density of the plasma and enhance the sputtering rate from a frontface of the target. Magnets used in the magnetron are typically closedloop for DC sputtering and open loop for RF sputtering.

In plasma enhanced substrate processing systems, such as physical vapordeposition (PVD) chambers, high power density PVD sputtering with highmagnetic fields and high DC power can produce high energy at asputtering target, and cause a large rise in surface temperature of thesputtering target. The sputtering target is cooled by contacting atarget backing plate with cooling fluid. In plasma sputtering astypically practiced commercially, a target of the material to be sputterdeposited is sealed to a vacuum chamber containing the wafer to becoated. Argon is admitted to the chamber. In the sputtering processes,the sputtering target is bombarded by energetic ions, such as a plasma,causing material to be displaced from the target and deposited as a filmon a substrate placed in the chamber. The manufacture of EUV mask blanksincludes the deposition by PVD of a multilayer stack of alternatinglayers of two materials, such as silicon and molybdenum on a lowexpansion substrate. The multilayer stack is reflective of EUV light,which is generally in the 5 to 100 nanometer wavelength range.

There remains a need to reduce defect sources such as particles andcross-contamination of targets of different material in a multi-cathodePVD chamber. In addition, there is a need to improve reflectivity of themultilayer stack at EUV wavelengths such as at 13.5 nm.

SUMMARY

In a first aspect of the disclosure, method of manufacturing an extremeultraviolet (EUV) mask blank comprises forming a reflective layer paircomprising silicon and molybdenum, wherein forming the reflective layerpair comprises: (a) sputtering a silicon target in a physical vapordeposition (PVD) chamber using a DC power source and an flowing inertgas in the PVD chamber to form a silicon layer on a substrate; (b)sputtering the silicon target using an RF power source and flowingnitrogen gas in the PVD chamber to form a first Si₃N₄ interface layer onthe silicon layer and a Si₃N₄ layer on the silicon target; (c)sputtering a molybdenum target using a DC power source and flowing aninert gas in the PVD chamber to form a molybdenum layer on the Si₃N₄layer; (d) sputtering the silicon target including the Si₃N₄ layerthereon using a DC power source and flowing an inert gas in the PVDchamber to form a second Si₃N₄ interface layer on the molybdenum layeruntil the Si₃N₄ layer is depleted from silicon target and thendepositing a silicon layer on the second Si₃N₄ interface layer; andrepeating steps (b) through (d) to form a multilayer stack comprising aplurality of reflective layer pairs.

According to a second embodiment of the disclosure, a method comprisesmethod of manufacturing an EUV mask blank comprising forming areflective layer pair comprising silicon and molybdenum, wherein formingthe reflective layer pair comprises (a) sputtering a silicon target in aphysical vapor deposition (PVD) chamber using a DC power source and anflowing inert gas in the PVD chamber to form a silicon layer on asubstrate; (b) sputtering the silicon target using an RF power sourceand flowing nitrogen gas in the PVD chamber to form a first Si₃N₄interface layer on the silicon layer and a Si₃N₄ layer on the silicontarget; (c) sputtering a molybdenum target using a DC power source andflowing an inert gas in the PVD chamber to form a molybdenum layer onthe Si₃N₄ layer; (d) sputtering the silicon target including the Si₃N₄layer thereon using a DC power source and flowing an inert gas in thePVD chamber to form a second Si₃N₄ interface layer on the molybdenumlayer until the Si₃N₄ layer is depleted from silicon target and thendepositing a silicon layer on the second Si₃N₄ interface layer;repeating steps (b) through (d) to form a multilayer stack comprising aplurality of reflective layer pairs comprising 40 reflective layerpairs; forming a capping layer on the multilayer stack; and forming anabsorber layer on the capping layer.

A third embodiment of the disclosure pertains to an extreme ultraviolet(EUV) mask blank comprising a substrate; a multilayer stack whichreflects EUV radiation, the multilayer stack comprising a plurality ofreflective layer pair including a silicon layer and a molybdenum layer,and an interface layer between the silicon layer and the molybdenumlayer, the interface layer comprising Si₃N₄; a capping layer on themultilayer stack of reflecting layers; and an absorber layer on thecapping layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a side view of a prior art deposition system;

FIG. 2 is a side view of a PVD chamber according to one or moreembodiments;

FIG. 3 is a bottom isometric view of the upper shield of the PVD chamberof FIG. 2; and

FIG. 4A is bottom view of the upper shield and targets in a firstrotational position;

FIG. 4B is a bottom view of the upper shield and the targets in a secondrotational position;

FIG. 4C is a bottom view of the upper shield and the targets in a thirdrotational position;

FIG. 5A is a bottom view of the upper shield and targets for in a firstrotational position for a deposition process;

FIG. 5B is a bottom view of the upper shield and targets in a secondrotational position for a pasting process; and

FIG. 6A is a schematic of a portion of a process showing deposition of asilicon layer on a substrate;

FIG. 6B is a schematic of a portion of a process showing deposition of afirst silicon nitride interface layer on the silicon layer deposited asshown in FIG. 6A;

FIG. 6C is a schematic of a portion of a process showing deposition of amolybdenum layer on the first silicon nitride interface layer depositedas shown in FIG. 6B;

FIG. 6D is deposition of a second silicon nitride interface layer on themolybdenum layer deposited as shown in FIG. 6A followed by deposition ofa silicon layer; and

FIG. 7 is a schematic view of a multilayer structure according to anembodiment of the disclosure.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate can also refer to only a portion of thesubstrate, unless the context clearly indicates otherwise. Additionally,reference to depositing on a substrate can mean both a bare substrateand a substrate with one or more films or features deposited or formedthereon

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOI), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/orbake the substrate surface. In addition to film processing directly onthe surface of the substrate itself, in the present disclosure, any ofthe film processing steps disclosed may also be performed on anunderlayer formed on the substrate as disclosed in more detail below,and the term “substrate surface” is intended to include such underlayeras the context indicates. Thus, for example, where a film/layer orpartial film/layer has been deposited onto a substrate surface, theexposed surface of the newly deposited film/layer becomes the substratesurface.

The term “horizontal” as used herein is defined as a plane parallel tothe plane or surface of a mask blank, regardless of its orientation. Theterm “vertical” refers to a direction perpendicular to the horizontal asjust defined. Terms, such as “above”, “below”, “bottom”, “top”, “side”(as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, aredefined with respect to the horizontal plane, as shown in the figures.

The term “on” indicates that there is direct contact between elements.The term “directly on” indicates that there is direct contact betweenelements with no intervening elements.

Those skilled in the art will understand that the use of ordinals suchas “first” and “second” to describe process regions do not imply aspecific location within the processing chamber, or order of exposurewithin the processing chamber.

Embodiments of the disclosure pertain to a magnet design for adeposition system, for example a physical vapor deposition (“PVD”)chamber comprising at least one cathode assembly, and in particularembodiments, a PVD chamber comprising multiple cathode assemblies(referred to herein as a “multi-cathode chamber).

FIG. 1 shows a prior art PVD system, in which a side view of a portionof a deposition system in the form of a PVD chamber 100 is shown. Thedeposition system in the form of a PVD chamber is shown as amulti-cathode PVD chamber 100 including a plurality of cathodeassemblies 102. The multi-cathode PVD chamber 100 is shown as includinga multi-target PVD source configured to manufacture an MRAM(magnetoresistive random access memory) or a multi-target PVD sourceconfigured to manufacture an extreme ultraviolet (EUV) mask blank, forexample a target comprising silicon and a target comprising molybdenumto form a multilayer stack reflective of EUV light.

The multi-cathode PVD chamber comprises a chamber body 101, comprisingan adapter (not shown) configured to hold a plurality of cathodeassemblies 102 in place in a spaced apart relationship. Themulti-cathode PVD chamber 100 can include a plurality of cathodeassemblies 102 for PVD and sputtering. Each of the cathode assemblies102 is connected to a power supply 112, including direct current (DC)and/or radio frequency (RF).

The cross-sectional view depicts an example of a PVD chamber 100including the chamber body 101 defining an inner volume 121, where asubstrate or carrier is processed. The cathode assemblies 102 in theembodiment shown in FIG. 1 can be used for sputtering differentmaterials as a material layer 103. The cathode assemblies 102 exposedthrough shield holes 104 of an upper shield 106, which is disposed overthe substrate or carrier 108 on a rotating pedestal 110. The uppershield 106 is generally conical in shape. There may generally be onlyone carrier 108 over or on the rotating pedestal 110.

The substrate or carrier 108 is shown as a structure having asemiconductor material used for fabrication of integrated circuits. Forexample, the substrate or carrier 108 comprises a semiconductorstructure including a wafer. Alternatively, the substrate or carrier 108can be another material, such as an ultra low expansion glass substrateused to form an EUV mask blank. The substrate or carrier 108 can be anysuitable shape such as round, square, rectangular or any other polygonalshape.

The upper shield 106 is formed with the shield holes 104 so that thecathode assemblies 102 can be used to deposit the material layers 103through the shield holes 104. A power supply 112 is applied to thecathode assemblies 102. The power supply 112 can include a directcurrent (DC) or radio frequency (RF) power supply.

The upper shield 106 is configured to expose one of the cathodeassemblies 102 at a time and protect other cathode assemblies 102 fromcross-contamination. The cross-contamination is a physical movement ortransfer of a deposition material from one of the cathode assemblies 102to another of the cathode assemblies 102. The cathode assemblies 102 arepositioned over targets 114. A design of a chamber can be compact. Thetargets 114 can be any suitable size. For example, each of the targets114 can be a diameter in a range of from about 4 inches to about 20inches, or from about 4 inches to about 15 inches, or from about 4inches to about 10 inches, or from about 4 inches to about 8 inches orfrom about 4 inches to about 6 inches.

In FIG. 1, the substrate or carrier 108 is shown as being on therotating pedestal 110, which can vertically move up and down. Before thesubstrate or carrier 108 moves out of the chamber, the substrate orcarrier 108 can move below a lower shield 118. A telescopic cover ring120 abuts the lower shield 118. Then, the rotating pedestal 110 can movedown, and then the carrier 108 can be raised with a robotic arm beforethe carrier 108 moves out of the chamber.

When the material layers 103 are sputtered, the materials sputtered fromthe targets 114 can be retained inside and not outside of the lowershield 118. In this prior art embodiment, telescopic cover ring 120includes a raised ring portion 122 that curves up and has a predefinedthickness. The telescopic cover ring 120 can also include a predefinedgap 124 and a predefined length with respect to the lower shield 118.Thus, the materials that form material layers 103 will not be below therotating pedestal 110 thereby eliminating contaminants from spreading tothe substrate or carrier 108.

FIG. 1 depicts individual shrouds 126. The shrouds 126 can be designedsuch that a majority of the materials from the targets 114 that does notdeposit on the carrier 108 is contained in the shrouds 126, hence makingit easy to reclaim and conserve the materials. This also enables one ofthe shrouds 126 for each of the targets 114 to be optimized for thattarget to enable better adhesion and reduced defects.

The shrouds 126 can be designed to minimize cross-talk or cross-targetcontamination between the cathode assemblies 102 and to maximize thematerials captured for each of the cathode assemblies 102. Therefore,the materials from each of the cathode assemblies 102 would just beindividually captured by one of the shrouds 126 over which the cathodeassemblies 102 are positioned. The captured materials may not bedeposited on the substrate or carrier 108. For example, a first cathodeassembly and a second cathode assembly can apply alternating layers ofdifferent materials in the formation of an extreme ultraviolet maskblank, for example, alternating layers of silicon deposited from a firsttarget and cathode assembly 102 and a molybdenum from a second targetand cathode assembly 102.

The substrate or carrier 108 can be coated with uniform material layer103 deposited on a surface of the substrate or carrier 108 using thedeposition materials including a metal from the targets 114 over theshrouds 126. Then, the shrouds 126 can be taken through a recoveryprocess. The recovery process not only cleans the shrouds 126 but alsorecovers a residual amount of the deposition materials remained on or inthe shrouds 126. For example, there may be molybdenum on one of theshrouds 126 and then silicon on another of the shrouds 126. Sincemolybdenum is more expensive than silicon, the shrouds 126 withmolybdenum can be sent out for the recovery process.

As shown in FIG. 1, the lower shield 118 is provided with a first bendresulting from small angle 130 and a second bend resulting from largeangle 132, which result in a knee 119 in the lower shield 118. This knee119 provides an area in which particles can accumulate duringdeposition, and is thus a possible source for processing defects.

PVD chambers and processes are utilized to manufacture extremeultraviolet (EUV) mask blanks. An EUV mask blank is an optically flatstructure used for forming a reflective mask having a mask pattern. Thereflective surface of the EUV mask blank forms a flat focal plane forreflecting the incident light, such as the extreme ultraviolet light. AnEUV mask blank comprises a substrate providing structural support to anextreme ultraviolet reflective element such as an EUV reticle. Thesubstrate is made from a material having a low coefficient of thermalexpansion (CTE) to provide stability during temperature changes, forexample, a material such as silicon, glass, oxides, ceramics, glassceramics, or a combination thereof.

Extreme ultraviolet (EUV) lithography, also known as soft x-rayprojection lithography, can be used for the manufacture of 0.0135 micronand smaller minimum feature size semiconductor devices. However, extremeultraviolet light, which is generally in the 5 to 100 nanometerwavelength range, is strongly absorbed in virtually all materials. Forthat reason, extreme ultraviolet systems work by reflection rather thanby transmission of light. Through the use of a series of mirrors, orlens elements, and a reflective element, or a mask blank, coated with anon-reflective absorber mask pattern, the patterned actinic light isreflected onto a resist-coated semiconductor substrate.

The lens elements and mask blanks of extreme ultraviolet lithographysystems are coated with reflective multilayer stack of coatings ofalternating reflective layers of materials such as molybdenum andsilicon. Reflection values of approximately 65% per lens element or maskblank have been obtained by using substrates that are coated withmultilayer coatings that strongly reflect extreme ultraviolet lightwithin an extremely narrow ultraviolet bandpass, for example, 12.5 to14.5 nanometer bandpass for 13.5 nanometer ultraviolet light. During themanufacture of EUV mask blanks and lens elements, minimization ofdefects such as defects from particle sources and high reflectivity ofthe reflective multilayer stack are generally desired.

FIG. 2 depicts a PVD chamber 200 in accordance with a first embodimentof the disclosure. PVD chamber 200 includes a plurality of cathodeassemblies 202 a and 202 b. While only two cathode assemblies 202 a and202 b are shown in the side view of FIG. 2, a multicathode chamber cancomprise more than two cathode assemblies, for example, five, six ormore than six cathode assemblies. An upper shield 206 is provided belowthe plurality of cathode assemblies 202 a and 202 b, the upper shield206 having two shield holes 204 a and 204 b to expose targets 205 a, 205b disposed at the bottom of the cathode assemblies 202 a to the interiorspace 221 of the PVD chamber 200. A middle shield 216 is provided belowand adjacent upper shield 206, and a lower shield 218 is provided belowand adjacent upper shield 206.

A modular chamber body is disclosed in FIG. 2, in which an intermediatechamber body 225 is located above and adjacent a lower chamber body 227.The intermediate chamber body 225 is secured to the lower chamber body227 to form the modular chamber body, which surrounds lower shield 218and the middle shield. A top adapter lid 273 (shown in FIG. 8) isdisposed above intermediate chamber body 225 to surround upper shield206.

PVD chamber 200 is also provided with a rotating pedestal 210 similar torotating pedestal 110 in FIG. 1. A person of ordinary skill will readilyappreciate that other components of a PVD chamber, such as thosereferenced above in FIG. 1 but omitted in FIG. 2 for the sake ofclarity, are provided in PVD chamber 200 according to one or moreembodiments. It will be appreciated that the upper shield 206 of the PVDchamber 200 of FIG. 2 is substantially flat, compared to the conicalupper shield 106 of FIG. 1.

Thus, a first aspect of the disclosure pertains to a PVD chamber 200,which comprises a plurality of cathode assemblies including a firstcathode assembly 202 a including a first backing plate 210 a configuredto support a first target 205 a during a sputtering process and a secondcathode assembly 202 b including a second backing plate 210 b configuredto support a second target 205 b during a sputtering process. The PVDchamber further comprises an upper shield 206 below the plurality ofcathode assemblies 202 a, 202 b having a first shield hole 204 a havinga diameter D1 and positioned on the upper shield to expose the firstcathode assembly 202 a and a second shield hole 204 b having a diameterD2 and positioned on the upper shield 206 to expose the second cathodeassembly 202 b, the upper shield 206 having a substantially flat insidesurface 203, except for a region 207 between the first shield hole 204 aand the second shield hole 204 b.

The upper shield 206 includes a raised area 209 in the region 207between the first shield hole and the second shield hole, the raisedarea 209 having a height “H” from the substantially flat inside surface203 that greater than one centimeter from the flat inside surface 203(best seen in FIG. 1) and having a length “L” greater than the diameterD1 of the first shield hole 204 a and the diameter D2 of the secondshield hole 204 b, wherein the PVD chamber is configured to alternatelysputter material from the first target 205 a and the second target 205 bwithout rotating the upper shield 206.

In one or more embodiments, the raised area 209 has a height H so thatduring a sputtering process, the raised area height H is sufficient toprevents material sputtered from the first target 205 a from beingdeposited on the second target 205 b and to prevent material sputteredfrom the second target 205 b from being deposited on the first target205 a.

According to one or more embodiments of the disclosure, the firstcathode assembly 202 a comprises a first magnet spaced apart from thefirst backing plate 210 a at a first distance d1 and the second cathodeassembly 202 b comprises a second magnet 220 b spaced apart from thesecond backing plate 210 b at a second distance d2, wherein the firstmagnet 220 a and the second magnet 220 b are movable such that the firstdistance d1 can be varied (as indicated by arrow 211 a) and the seconddistance d2 can be varied (as indicated by arrow 211 b. The distance d1and the distance d2 can be varied by linear actuator 213 a to change thedistance d1 and linear actuator 213 b to change the distance d2. Thelinear actuator 213 a and the linear actuator 213 b can comprise anysuitable device that can respectively effect linear motion of firstmagnet assembly 215 a and second magnet assembly 215 b. First magnetassembly 215 a includes rotational motor 217 a, which can comprise aservo motor to rotate the first magnet 220 a via shaft 219 a coupled torotational motor 217 a. Second magnet assembly 215 b includes rotationalmotor 217 b, which can comprise a servo motor to rotate the secondmagnet 220 b via shaft 219 b coupled to rotational motor 217 b. It willbe appreciated that the first magnet assembly 215 a may include aplurality of magnets in addition to the first magnet 220 a. Similarly,the second magnet assembly 215 b may include a plurality of magnets inaddition to the second magnet 220 b.

In one or more embodiments, wherein the first magnet 220 a and secondmagnet 220 b are configured to be moved to decrease the first distanced1 and the second distance d2 to increase magnetic field strengthproduced by the first magnet 220 a and the second magnet 220 b and toincrease the first distance d1 and the second distance d2 to decreasemagnetic field strength produced by the first magnet 220 a and thesecond magnet 220 b.

In some embodiments, the first target 205 a comprises a molybdenumtarget and the second target 205 b comprises a silicon target, and thePVD chamber 200 further comprises a third cathode assembly (not shown)including a third backing plate to support a third target 205 c (seeFIGS. 4A-C) and a fourth cathode assembly (not shown) including a fourthbacking plate configured to support a fourth target 205 d (see FIGS.4A-C). The third cathode assembly and fourth cathode assembly accordingto one or more embodiments are configured in the same manner as thefirst and second cathode assemblies 202 a, 202 b as described herein. Insome embodiments, the third target 205 c comprises a dummy target andthe fourth target 205 d comprises a dummy target. As used herein, “dummytarget” refers to a target that is not intended to be sputtered in thePVD apparatus 200.

Referring now to FIGS. 4A-C, the first target 205 a, the second target205 b, the third target 205 c and the fourth target 205 d are positionedwith respect to each other and the first shield hole 204 a and secondshield hold 204 b so that. In the embodiment shown, first target(positioned under first cathode assembly 202 a) is at position P1, thesecond target 205 b (positioned under second cathode assembly 202 b) isat position P2. In some embodiments, the raised area 209 is positionedbetween first shield hold 204 a and second shield hole 204 b. In theembodiment shown, the first shield hole 204 a and the second shield hole204 b are positioned with respect to the first target 205 a, the secondtarget 205 b, the third target 205 c and the fourth target 205 d tofacilitate cleaning of the first target 205 a and the second target 205b.

In use, the PVD chamber according to one or more embodiments operates asfollows during a deposition process. The first shield hole 204 a ispositioned to expose the first target, and the second shield hole 204 bis positioned to expose the second target 205 b. The first target 205 aand the second target 205 b are comprised of different materials. In aspecific embodiment of the disclosure, the first target 205 a comprisesmolybdenum and the second target 205 b comprises silicon. During adeposition process, material is alternately sputtered from the firsttarget 205 a and the second target 205 b to form a multilayer stack ofalternating materials layers where adjacent layers comprise differentmaterials. Deposition of the alternating layers of materials from thefirst target 205 a and the second target 205 b occurs without rotatingthe upper shield 206, which reduces generation of particulate comparedto an apparatus with a single shield hole in which the upper shield mustbe rotated to accomplish alternate deposition of different materials toform a multilayer stack comprised of two different materials. In one ormore embodiments, the alternating layers comprise silicon and molybdenumto form a multilayer stack that is reflective of EUV light. FIG. 4Adepicts the position of the first target 205 a in position P1 and target205 b at position P2. In some embodiments, the upper shield comprises araised area 209 in the region 207 between the first shield hold 204 aand the second shield hole 204 b.

In the embodiment shown, the upper shield 206 is circular, and thecenter of the first shield hole 204 a at the first position P1, and thesecond position P2 where the center of the second shield hole 204 b islocated is 150 degrees in a counterclockwise direction indicated byarrow 261 from the center of the first shield hole 204 a. Likewise, thecenter of target 205 a and the center of the second target 205 b atpositions P1 and P2, which are 150 degrees apart from each other. InFIG. 4A third target 205 c and fourth target 205 d are dummy targetswhich are covered by the flat inside surface of the upper shield 206 andshown with their outlines as dotted lines.

FIG. 4B shows the position of the first shield hold 204 a as positionedover second target 205 b and the second shield hold 204 b as positionedover fourth target 205 d, which is a dummy target. The shield holes 204a and 204 b have been rotated counterclockwise 150 degrees from thedeposition position of FIG. 4A. The position of the first shield hole atposition P4 is over the fourth target 205 d, the center of which islocated 300 degrees counterclockwise from the center of the first target205 a. The second shield hole 204 b is now located over the secondtarget 205 b, the center of which is located 150 degreescounterclockwise from the center of the first target 205 a. It will beunderstood by a person of ordinary skill in the art that the positionsof the individual targets are fixed with respect to their respectivecathode assemblies, while the upper shield 206 is rotated over thetargets. FIG. 4B is a cleaning position, in which the second target 205b can be cleaned using a plasma. An advantage of cleaning in the mannershows in FIG. 4B where the second shield hole 204 b is positioned toexpose a dummy target (fourth target 205 d) while the first shield holeexposes the second target 205 b is that cleaning of the second targetcan be conducted while the first target 205 a is covered (as indicatedby the dashed line), and the first target 205 a will not be contaminatedby the cleaning process which removes contaminants from the secondtarget, which is a different material from the first target. Inaddition, the fourth target 205 d, which is a dummy target prevents thematerial which has been cleaned from the second target 205 b fromtravelling through an open shield hole (the second shield hole 204 b)and contaminating the chamber, namely the top adapter lid 273.

FIG. 4C shows the position of the shield holes 204 a and 204 b afterrotation counterclockwise 60 degrees, as indicated by arrow 260 in FIG.4B. In this position, the second shield hole, which has now been rotated210 degrees from the deposition position shown in FIG. 4A is nowpositioned over the first target 205 a at position P1, and the firstshield hole 204 a is now positioned over the third target 205 c, whichis a dummy target. The second target 205 b and the fourth target 205 d,both shown as dashed lines, are now covered by the upper shield. In theposition shown in FIG. 4C, the first target 205 a is exposed through thesecond shield hole 204 b and the third target 205 c is exposed by thefirst shield hole 204 a. The first target 205 a can be cleaned in acleaning process with a plasma

Summarizing FIGS. 4A-C, by spacing electrode assemblies and theassociated targets at the periphery of a multicathode chamber in themanner shown and using a rotatable upper shield comprising two shieldholes spaced from each other at the periphery of the upper shield asshown, the first target 205 a and the second target 205 b can be cleanedusing a plasma process in a PVD chamber. In one or more embodiments,when the third target 205 c and the fourth target 205 d are dummytargets that are not intended to be sputtered as part of depositionprocess, the dummy targets prevent contamination of the chamber duringcleaning of the first target 205 a and the second target 205 b. In someembodiments, the dummy targets comprise a side and front surface (thesurface facing the PVD chamber and substrate in the PVD chamber) aretextured to ensure no particle generation after large amount ofdeposition of material which has been cleaned from the first target 205a and the second target 205 b. In some embodiments, the textured surfaceis provided by arc spraying.

In the specific embodiment shown, the upper shield 206 is circular, andtwo shield holes are spaced at the outer periphery of the upper shield206 at the shield hole centers so that when the upper shield 206 isrotated with respect to the PVD chamber 200, the shield holes expose twotargets (either deposition targets such as first target 205 a and thesecond target 205 b). The first shield hole 204 a and the second shieldhole are spaced apart by their centers by 150 degrees on the outerperiphery of the upper shield 206, and indicated by arrow 261 in FIG.4A.

In the embodiment shown, at least four cathode assemblies and targetsbelow the cathode assemblies are spaced around the outer periphery ofthe of PVD chamber top adapter lid 273 so that when the upper shield 206is rotated, two different targets are exposed each time the upper shieldis rotated. In FIGS. 4A-C, the center of second target 205 b, which iscircular, is 150 degrees in a counterclockwise direction from the centerof the first target 205 a, which is also circular. Additionally, thecenter of third target 205 c, which is circular and a dummy target is210 degrees in a counterclockwise direction from the center of the firsttarget 205 a, and the center of fourth target 205 d, which is circularand a dummy target is 300 degrees in a counterclockwise direction fromthe first target. By arranging the targets in this manner on the topadapter lid 273 and the upper shield 206 having the centers of theshield holes 204 a and 204 b spaced apart by 250 degrees, but rotatingthe upper shield 206, the first and second targets 205 a, 205 b can bothbe exposed during a deposition process, and then during a cleaningprocess the second target 205 b and a dummy target can be exposed toclean the second target and the first target 205 a and another dummytarget can be exposed to clean the first target 205 a while the otherdeposition target is not subject to contamination from cleaning of thetarget.

Stated another way, in one or more embodiments, the third target 205 cand the fourth target 205 d are positioned with respect to the firsttarget 205 a and second target 205 b so that when the upper shield 206is in a first position, the first target 205 a is exposed through thefirst shield hole 204 a and the second target 205 b is exposed throughthe second shield hole 204 b, and the third target 205 c and fourthtarget 205 d are covered by the upper shield 206. When the upper shield206 is rotated to a second position, the fourth target 205 d is exposedthrough the second shield hole 204 b and the second target 205 b isexposed through the first shield hole 204 a. In some embodiments, whenthe upper shield 206 is rotated to a third position, the first target205 is exposed through the second shield hole 204 b and the fourthtarget 205 d is exposed through the first shield hole 204 a.

In another embodiment, a physical vapor deposition (PVD) chamber 200comprises a plurality of cathode assemblies including a first cathodeassembly 202 a including a first backing plate 210 a supporting a firsttarget 205 a comprising molybdenum and a second cathode assembly 202 bincluding a second backing plate 210 b supporting a second target 205 bcomprising silicon, a third cathode assembly including a third backingplate supporting a third target 205 c comprising a dummy material, and afourth cathode assembly including a fourth backing plate supporting afourth target 205 d comprising a dummy material. In this embodiment, anupper shield 206 is below the plurality of cathode assemblies having afirst shield hole 204 a having a diameter D and positioned on the uppershield to expose the first target 205 a and a second shield hole 204 bhaving a diameter D and positioned on the upper shield to expose thesecond target 205, the upper shield 206 having a flat inside surface 203between the first shield hole 204 a and the second shield hole 204 b andconfigured to permit molybdenum and silicon material to be alternatelysputtered from the first target 205 a and the second target 205 brespectively without rotating the upper shield 206. In this embodiment,the upper shield 206 includes a raised area 209 between the two of theshield holes having a height H greater than one centimeter and having alength greater than the diameter D of the first shield hole 204 a andthe second shield hole 204 b, wherein the upper shield 206 is rotatableto allow one of the first shield hole 204 a and the second shield hole204 b to expose the first target 205 a and one of third target 205 c andthe fourth target 205 d.

In some embodiments, each of the first cathode assembly, the secondcathode assembly, third cathode assembly and fourth cathode assemblycomprise a magnet spaced apart from the first backing plate at a firstdistance, the second backing plate at a second distance, the thirdbacking plate at a third distance and the fourth backing plate at afourth distance, each of the magnets being movable to increase ordecrease each of the first distance, the second distance, third distanceor fourth distance. Decreasing the first distance, the second distance,the third distance or the fourth distance increases magnetic fieldstrength produced by the magnet. Increasing the first distance, thesecond distance, the third distance or the fourth distance decreasesmagnetic field strength produced by the magnet.

Plasma sputtering may be accomplished using either DC sputtering or RFsputtering in the PVD chamber 200. In some embodiments, the processchamber includes a feed structure for coupling RF and DC energy to thetargets associated with each cathode assembly. For cathode assembly 202a, a first end of the feed structure can be coupled to an RF powersource 248 a and a DC power source 250 a, which can be respectivelyutilized to provide RF and DC energy to the target 205 a. The RF powersource 248 a is coupled to RF power in 249 a and the DC power source 250a is coupled to DC power in 251 a. For example, the DC power source 250a may be utilized to apply a negative voltage, or bias, to the target305 a. In some embodiments, RF energy supplied by the RF power source248 a may range in frequency from about 2 MHz to about 60 MHz, or, forexample, non-limiting frequencies such as 2 MHz, 13.56 MHz, 27.12 MHz,40.68 MHz or 60 MHz can be used. In some embodiments, a plurality of RFpower sources may be provided (i.e., two or more) to provide RF energyin a plurality of the above frequencies.

Likewise, for cathode assembly 202 b, a first end of the feed structurecan be coupled to an RF power source 248 b and a DC power source 250 b,which can be respectively utilized to provide RF and DC energy to thetarget 205 b. The RF power source 248 b is coupled to RF power in 249 aand the DC power source 250 b is coupled to DC power in 251 b. Forexample, the DC power source 250 b may be utilized to apply a negativevoltage, or bias, to the target 205 b. In some embodiments, RF energysupplied by the RF power source 248 b may range in frequency from about2 MHz to about 60 MHz, or, for example, non-limiting frequencies such as2 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz or 60 MHz can be used. In someembodiments, a plurality of RF power sources may be provided (i.e., twoor more) to provide RF energy in a plurality of the above frequencies.

While the embodiment shown includes separate RF power sources 248 a and248 b for cathode assemblies 202 a and 202 b, and separate DC powersources 250 a and 250 b for cathode assemblies 202 a and 202 b, the PVDchamber can comprise a single RF power source and a single DC powersource with feeds to each of the cathode assemblies.

Another aspect of the disclosure pertains to a method of depositingalternating material layers in a physical vapor deposition (PVD)chamber. In one embodiment, the method comprises placing a substrate 270in the PVD chamber 200 comprising a plurality of cathode assembliesincluding a first cathode assembly 202 a including a first target 205 acomprising a first material and a second cathode assembly 202 bincluding a second target 205 b comprising a second material differentfrom the first material. The method further comprises disposing an uppershield 206 below the plurality of cathode assemblies, the upper shieldhaving a first shield hole 204 a having a diameter D1 and positioned onthe upper shield 206 to expose the first target 205 a and a secondshield hole 204 b having a diameter D2 and positioned on the uppershield 206 to expose the second target 205 b, the upper shield 206further comprising a flat inside surface 203 between the first shieldhole 204 a and the second shield hole 204 b and a raised area 209 in aregion 207 between the two of the shield holes 204 a, 204 b having alength L at least equal to the diameter D1 of the first shield hole andthe second shield hole D2. In some embodiments, the raised area 209 hasa height H greater than one centimeter. The method further comprisesalternately sputtering material from the first target 204 a and thesecond target 204 b without rotating the upper shield 206, wherein theraised area prevents the first material from contaminating the secondtarget and prevents the second material from contaminating the firsttarget.

In some embodiments of the method, the PVD chamber further comprises athird target 205 c comprising dummy material and a fourth target 205 dcomprising dummy material and wherein third target 205 c and the fourthtarget 205 d are positioned with respect to the first target 205 a andsecond target 205 b so that when the upper shield 206 is in a firstposition, the first target 205 a is exposed through the first shieldhole 204 a and the second target 205 b is exposed through the secondshield hole 204 b, and the third target 205 c and fourth target 205 dare covered by the upper shield 206 during depositing alternatingmaterial layers from the first target 205 a and the second target 205 b.

In some embodiments of the method, the method further comprises cleaningfirst material deposited on the second target 205 b by applying amagnetic field to the second target that is greater than a magneticfield applied during depositing alternating material layers. In someembodiments, the method further comprises comprising cleaning secondmaterial deposited on the first target 205 a by applying a magneticfield to the first target that 205 a is greater than a magnetic fieldapplied during depositing alternating material layers.

In some embodiments, the method further comprises rotating the uppershield 206 from the first position to a second position prior tocleaning the first material from the second target 205 b, the fourthtarget 205 d is exposed through the second shield hole 204 b and thesecond target 205 b is exposed through the first shield hole 204 a. Inone or more embodiments, the method comprises rotating the upper shield206 from the second position to a third position so that the firsttarget 205 a is exposed through the second shield hole 204 b and thefourth target 205 d is exposed through the first shield hole 204 a. Inspecific embodiments of the method, the substrate 270 comprises anextreme ultraviolet (EUV) mask blank. In specific embodiments of themethod the first target material comprises molybdenum and the secondtarget material comprises silicon. In some embodiments, the methodfurther comprises depositing multiple alternating materials layerscomprising a first layer comprising molybdenum and a second layercomprising silicon.

In another aspect of the disclosure, the targets associated with thefirst cathode assembly, the second cathode assembly, the third cathodeassembly and the fourth cathode assembly are comprised of material topermit a co-sputtering and pasting process.

A benefit of the upper shield with the first shield hole 204 a and thesecond shield hole arranged in the upper shield according to embodimentsdescribed herein include the ability to deposit alternating layers ofdifferent materials without rotating the upper shield. In someembodiments, after completion of a process of depositing a multilayerstack on a substrate, the upper shield can be rotated as described aboveto conduct a cleaning operation in which one of the shield holes ispositioned over a dummy target.

In some embodiments, a target configuration can be used to perform amultilayer stack deposition process on a substrate while the shield isnot rotated by alternately sputtering material from the first and secondtarget, and then by rotating the shield, a pasting process can beconducted to paste material on the interior of the PVD chamber. It wasdetermined that when two different materials are deposited from a firstand second target, for example, molybdenum from a first target andsilicon from a second target, material from the second target (e.g.,silicon) may accumulate near the shield hole that was over the secondtarget, cause a second material rich defect source (e.g., Si-rich defectsource). The second material rich defect source in some embodimentscauses second material defects (e.g. Si defects). It was determined thatby pasting the interior of the PVD chamber, namely the upper shield,206, the middle shield 216, and the lower shield 218 with the firstmaterial, e.g., molybdenum, second material defects (e.g., Si defects)could be reduced or prevented. The upper shield comprising a firstshield hole and a second shield hole according to embodiments describedherein facilitates a way to quickly conduct a pasting operation byrotating the upper shield to a position to conduct a pasting process.

Thus, with reference to FIGS. 2, 3, and 5A-B, one or more embodimentspertain to a physical vapor deposition (PVD) chamber 200 comprising aplurality of cathode assemblies including a first cathode assembly 202 aincluding a first backing plate 210 a to support a first target 205 acomprising a first material during a sputtering process and a secondcathode assembly 202 b including a second backing plate 210 b configuredto support a second target 205 b comprising a second material differentfrom the first material during a deposition process. The depositionprocess is conducted when there is a substrate 270 in the PVD chamber.The PVD chamber 200 further comprises an upper shield 206 below theplurality of cathode assemblies including a first shield hole 204 ahaving a diameter and positioned on the upper shield 206 and withrespect to the first and second cathode assemblies 202 a, 202 b toexpose the first target 205 a during a deposition process and a secondshield hole 204 b having a diameter and positioned on the upper shieldto expose the second target 205 b during a deposition process. The PVDchamber 200 is configured to alternately sputter the first material fromthe first target 205 a and the second material from the second target205 b onto a substrate in the PVD chamber 200 without rotating the uppershield 206.

In some embodiments, a third cathode assembly (not shown) includes athird backing plate and a third target 205 c comprising a third materialthat is the same as the first material and a fourth cathode assembly(not shown) including a backing plate and a fourth target 205 dcomprising a fourth material that is the same as the third material.

In some embodiments and ash shown in FIG. 5B, the upper shield 206 isrotatable from a first position in which the first target 205 a atposition P1 and the second target at position P2 are exposed during adeposition process. The PVD chamber is configured so that the uppershield 206 is rotatable to a second position in which the third targetat position P3 and the fourth target 205 d at position P4 are exposedfor a pasting process in which material from the third target 205 c andthe fourth target 205 d is pasted on the interior of the chamber whilethe first target 205 a and the second target are 205 b covered by theupper shield. As discussed above, such a configuration of the cathodeassemblies and targets 205 a, 205 b, 205 c, 205 d allows for pasting ofa first material such as molybdenum on the interior surface of the PVDchamber to reduce prevent defects from areas that generated from areasthat are rich in the second material (e.g., Si).

In one or more embodiments, the upper shield 206 has flat inside surface203, except for a region 207 between the first shield hole 204 a and thesecond shield hole 204 a and a raised area 209 in the region between thefirst shield hole 204 a and the second shield hole 204 a, the raisedarea 209 having a height H sufficient so that during a depositionprocess, the raised area 209 prevents material sputtered from the firsttarget 205 a from being deposited on the second target 205 b and toprevent material sputtered from the second target 205 b from beingdeposited on the first target 205 a. In one or more embodiments, theheight H of the raised area is at least 1 cm from the flat insidesurface 203 of the upper shield 206 a length L greater than the diameterof the first shield hole and the diameter of the second shield hole.

In some embodiments of the PVD chamber having the configuration oftargets shown in FIGS. 5A and 5B, The PVD chamber of claim 5, whereinthe first cathode assembly 202 a comprises a first magnet 220 a spacedapart from the first backing plate 210 a at a first distance d1 and thesecond cathode assembly 202 b comprises a second magnet 220 b spacedapart from the second backing plate 210 b at a second distance d2, andthe first magnet 220 a and the second magnet 220 b are movable such thatthe first distance d1 can be varied and the second distance d2 can bevaried. In specific embodiments, the first magnet 220 a and secondmagnet 220 b are configured to be moved to decrease the first distanceand the second distance to increase magnetic field strength produced bythe first magnet 220 a and the second magnet 220 b and to increase thefirst distance d1 and the second distance d2 to decrease magnetic fieldstrength produced by the first magnet 220 a and the second magnet 220 b.

Another embodiment of a PVD chamber having the target configurationshown in FIGS. 5A and 5B comprises a plurality of cathode assembliesincluding a first cathode assembly 202 a including a first backing plate210 a supporting a first target 205 a comprising molybdenum and a secondcathode 202 b assembly including a second backing plate 210 b supportinga second target 205 b comprising silicon, a third cathode assembly (notshown) including a third backing plate supporting a third target 205 ccomprising molybdenum, and a fourth cathode assembly (not shown)including a fourth backing plate supporting a fourth target 205 dcomprising molybdenum. The PVD chamber as configured further comprisesan upper shield 206 below the plurality of cathode assemblies having afirst shield hole 204 a having a diameter and positioned on the uppershield 206 to expose the first target 205 a and a second shield 204 bhole having a diameter and positioned on the upper shield 206 to exposethe second target 205 b when the upper shield 206 is in a firstposition, the upper shield 206 having a flat inside surface 203, exceptfor a region 207 between the first shield hole 204 a and the secondshield hole 204 b, the upper shield 206 positioned with respect to thefirst target 205 a and the second target 205 b and the PVD chamber topermit molybdenum and silicon material to be alternately sputtered fromthe first target and the second target respectively without rotating theupper shield 206. The upper shield of this embodiment includes a raisedarea 209 in the region 207 between the first shield hole 204 a and thesecond shield hole 204 b, the raised area 209 and having a length Lgreater than the diameter D1 of the first shield hole 204 a and thediameter D2 of the second shield hole 204 b, wherein the upper shield206 is rotatable to allow one of the first shield hole 204 a and thesecond shield hole 204 b to expose the first target 205 a and one ofthird target 205 c and the fourth target 205 d. The PVD chamber 200 mayfurther comprise a fifth cathode assembly (not shown) with a backingplate and a fifth target 205 e as shown in FIGS. 5A and 5B.

In a variant on this embodiments, the upper shield 206 is configured tobe rotated to a second position with respect to the first target 205 a,the second target 205 b, the third target 205 c and the fourth target205 d so that the second shield hole 204 b is over the third target 205c to expose the third target 205 c and the first shield hole 204 a isover the fourth target 205 d to expose the fourth target 205 d. Inanother variant on this embodiment, when the upper shield 206 is in thesecond position, the PVD chamber 200 is configured to perform a pastingoperation wherein molybdenum from the third target 205 c and the fourthtarget 205 d are pasted on the interior of the chamber and the firsttarget 205 a and the second target 205 b are covered by the upper shield206. This configuration is shown in FIG. 5B, with the first target 205 aand the second target 205 b shown as outlined by dashed lines.

Another aspect of the disclosure comprises method of depositingalternating material layers in a physical vapor deposition (PVD) chambercomprising operating a PVD chamber comprising a plurality of cathodeassemblies including a first cathode assembly 202 a including a firsttarget 205 a comprising a first material, a second cathode assembly 202b including a second target 205 b comprising a second material differentfrom the first material, a third cathode assembly including a thirdtarget 205 c comprising the same material as the first target, and afourth cathode assembly including a target 205 d comprising a materialthe same as the first target. The method further comprises disposing anupper shield 206 below the plurality of cathode assemblies, the uppershield having a first shield hole 204 a having a diameter D1 andpositioned on the upper shield 206 to expose the fourth target 205 d anda second shield hole having a diameter D2 and positioned on the uppershield to expose the third target 205 c. The method includes alternatelysputtering material from the third target 205 c and the fourth target205 d to deposit the third target material and the fourth targetmaterial on an interior of the PVD chamber. This configuration is shownin FIG. 5B.

Depositing material from the third target 205 c and the fourth target205 d prevents defects deposited from the first target 205 a fromcontaminating the interior of the PVD chamber. In some embodiments ofthe method, wherein the upper shield further comprises a flat insidesurface 203, except for a region 207 between the first shield hole 204 aand the second shield hole 204 b. In one embodiment, the region 207between the first shield hole 204 a and the second shield hole 204 bincludes a raised area 209 having a length L at least equal to thediameter D1 of the first shield hole 204 a and the diameter D2 of thesecond shield hole 204 b.

One or more embodiments of the method comprises rotating the uppershield 206 from the position in FIG. 5B to the position in FIG. 5A sothat the first shield hole 204 a is over the first target 205 a toexpose the first target 205 aa and the second shield hole 204 b is overthe second target 205 b to expose the second target 205 b. This can beaccomplished by rotating the upper shield 206 clockwise in the directionof arrow 262 by 150 degrees, or alternatively rotating the upper shieldcounterclockwise 210 degrees so that the first shield hole 204 a is overthe first target 205 a as shown in FIG. 5A.

After rotating to the position shown in FIG. 5A, the method of someembodiments comprises placing a substrate 270 in the chamber 200 andalternately sputtering material from the first target 205 a and thesecond target 205 b without rotating the upper shield 206, wherein theraised area 209 prevents the first material from contaminating thesecond target 205 b and prevents the second material from contaminatingthe first target 205 a.

In specific embodiments, the substrate 270 comprises an extremeultraviolet (EUV) mask blank. In such embodiments, the first targetmaterial comprises molybdenum and the second target material comprisessilicon. The method according to these embodiment may further comprisedepositing multiple alternating materials layers comprising a firstlayer comprising molybdenum and a second layer comprising silicon.

The configuration and spacing of the targets 205 a, 205 b, 205 c and 205d in FIGS. 5A and 5B, together with the shield holes 204 a, 204 b spacedas shown facilitates both deposition of alternating different materiallayers on a substrate in one process, and then, by rotating the uppershield degrees, pasting of molybdenum on the interior of the PVD chamber200 to prevent generation of defects from the second material (e.g.,silicon). As shown, the center of first target 205 a is spaced 150degrees from the center of the second target 205 b around periphery ofthe PVD chamber 200 top adapter lid 273. The center of third target 205c is spaced 150 degrees from the center of the fourth target 205 d.Since the first shield hole 204 a center and the second shield hole 204b centers are spaced 150 degrees around the periphery of the uppershield 206, when the upper shield is in a first position, the firstshield hole is at the location of the first target 205 a at position P1and the second shield hole 204 b is at position P2 over the secondtarget 205 b.

Because the center of the fourth target is spaced 90 degrees at theperiphery of the top adapter lid 27 from the center of the first target205 a and the third target 205 center is spaced 90 degrees around theperiphery of the top adapter lid 273 from the second target 205 b,rotation of the upper shield 206 in a clockwise direction will positionthe first shield hole 204 a and the second shield hole for a pastingprocess as described above.

In some embodiments, the methods described herein are conducted in thePVD chamber 200 equipped with a controller 290. There may be a singlecontroller or multiple controllers. When there is more than onecontroller, each of the controllers is in communication with each of theother controllers to control of the overall functions of the PVD chamber200. For example, when multiple controllers are utilized, a primarycontrol processor is coupled to and in communication with each of theother controllers to control the system. The controller is one of anyform of general-purpose computer processor, microcontroller,microprocessor, etc., that can be used in an industrial setting forcontrolling various chambers and sub-processors. As used herein, “incommunication” means that the controller can send and receive signalsvia a hard-wired communication line or wirelessly.

Each controller can comprise processor 292, a memory 294 coupled to theprocessor, input/output devices coupled to the processor 292, andsupport circuits 296 and 298 to provide communication between thedifferent electronic components. The memory includes one or more oftransitory memory (e.g., random access memory) and non-transitory memory(e.g., storage) and the memory of the processor may be one or more ofreadily available memory such as random access memory (RAM), read-onlymemory (ROM), floppy disk, hard disk, or any other form of digitalstorage, local or remote. The memory can retain an instruction set thatis operable by the processor to control parameters and components of thesystem. The support circuits are coupled to the processor for supportingthe processor in a conventional manner. Circuits may include, forexample, cache, power supplies, clock circuits, input/output circuitry,subsystems, and the like.

Processes may generally be stored in the memory as a software routinethat, when executed by the processor, causes the process chamber toperform processes of the present disclosure. The software routine mayalso be stored and/or executed by a second processor that is remotelylocated from the hardware being controlled by the processor. In one ormore embodiments, some or all of the methods of the present disclosureare controlled hardware. As such, in some embodiments, the processes areimplemented by software and executed using a computer system, inhardware as, e.g., an application specific integrated circuit or othertype of hardware implementation, or as a combination of software andhardware. The software routine, when executed by the processor,transforms the general purpose computer into a specific purpose computer(controller) that controls the chamber operation such that the processesare performed.

In some embodiments, the controller has one or more configurations toexecute individual processes or sub-processes to perform the method. Insome embodiments, the controller is connected to and configured tooperate intermediate components to perform the functions of the methods.

The PVD chambers 200 and methods described herein may be particularlyuseful in the manufacture of extreme ultraviolet (EUV) mask blanks. AnEUV mask blank is an optically flat structure used for forming areflective mask having a mask pattern. In one or more embodiments, thereflective surface of the EUV mask blank forms a flat focal plane forreflecting the incident light, such as the extreme ultraviolet light. AnEUV mask blank comprises a substrate providing structural support to anextreme ultraviolet reflective element such as an EUV reticle. In one ormore embodiments, the substrate is made from a material having a lowcoefficient of thermal expansion (CTE) to provide stability duringtemperature changes. The substrate according to one or more embodimentsis formed from a material such as silicon, glass, oxides, ceramics,glass ceramics, or a combination thereof.

An EUV mask blank includes a multilayer stack, which is a structure thatis reflective to extreme ultraviolet light. The multilayer stackincludes alternating reflective layers of a first reflective layer and asecond reflective layer. The first reflective layer and the secondreflective layer form a reflective pair. In a non-limiting embodiment,the multilayer stack includes a range of 20-60 of the reflective pairsfor a total of up to 120 reflective layers.

The first reflective layer and the second reflective layer can be formedfrom a variety of materials. In an embodiment, the first reflectivelayer and the second reflective layer are formed from silicon andmolybdenum, respectively. The multilayer stack forms a reflectivestructure by having alternating thin layers of materials with differentoptical properties to create a Bragg reflector or mirror. Thealternating layer of, for example, molybdenum and silicon are formed byphysical vapor deposition, for example, in a multi-cathode sourcechamber as described herein. In one or more embodiments, the chambersand the methods described herein can be used to deposit a multilayerstack of 20-60 reflective pairs of molybdenum and silicon. The uniquestructure of the upper shield with two shield holes enables depositionof a multilayer stack with fewer defects. The multicathode arrangementwith the targets including the dummy targets and second material targetas arranged in the embodiments described herein facilitates cleaning ofthe molybdenum and silicon targets and pasting of the interior of thechamber.

The PVD chambers 200 described herein are utilized to form themultilayer stack, as well as capping layers and absorber layers. Forexample, the physical vapor deposition systems can form layers ofsilicon, molybdenum, titanium oxide, titanium dioxide, ruthenium oxide,niobium oxide, ruthenium tungsten, ruthenium molybdenum, rutheniumniobium, chromium, tantalum, nitrides, compounds, or a combinationthereof. Although some compounds are described as an oxide, it isunderstood that the compounds can include oxides, dioxides, atomicmixtures having oxygen atoms, or a combination thereof.

Another aspect of the disclosure pertains to a method of manufacturingan EUV mask blank with a reflective layer stack exhibiting improvedreflectivity. A first embodiment of this method, with reference to FIGS.6A-D and FIG. 7 comprises forming a reflective layer pair comprisingsilicon and molybdenum. FIG. 6A schematically shows the step of formingthe silicon layer on the substrate. The substrate is placed in the PVDchamber 100 of FIG. 1 or the PVD chamber 200 of FIG. 2 as describedabove, or any chamber capable of sputtering silicon and molybdenum. Thechamber is supplied with a direct current (DC) power source and a radiofrequency (RF) power source, as shown with respect to the chamber inFIG. 2.

As shown in FIG. 6A, the first step in forming the reflective layer pairat 350A comprises sputtering a silicon target 305 a mounted to a backingplated 373 a in a physical vapor deposition (PVD) chamber using a DCpower source and an flowing inert gas in the PVD chamber to form asilicon layer 402 on a substrate 400. A person or ordinary skill in theart will understand that flowing the inert gas, for example, argon,causes the gas to be energized so that atoms from the silicon target areejected by momentum transfer from a bombarding argon gas ion energizedby the applied power. Gas can be supplied from any suitable gas sourcesuch as a cylinder of gas that is connected via a conduit to the chamberand delivered via a mass flow controller or a pressure controller.

After the silicon layer is deposited on the substrate 400, which can bea low expansion glass substrate, a first Si₃N₄ interface layer 403 a isformed on the silicon layer 402 at 350B as shown in FIG. 6B bysputtering the silicon target 305 a using an RF power source and flowingnitrogen gas in the PVD chamber to form the first Si₃N₄ interface layeron the silicon layer and a Si₃N₄ layer 403 on the silicon target.

As shown in FIG. 6C, at 350C a molybdenum layer 404 is formed on thefirst Si₃N₄ interface layer 403 a by sputtering a molybdenum target 305b mounted to a backing plate 373 b using a DC power source and flowingan inert gas such as nitrogen in the PVD chamber to form the molybdenumlayer 404 on the first Si₃N₄ interface layer 403 a. As shown in FIG. 6D,the next step in 350D includes sputtering the silicon target 305 aincluding the Si₃N₄ layer thereon using a DC power source and flowing aninert gas such as in the PVD chamber to form a second Si₃N₄ interfacelayer 403 b on the molybdenum layer 404 until the Si₃N₄ layer isdepleted from silicon target. After the Si₃N₄ layer is depleted fromsilicon target, a silicon layer is deposited on the second Si₃N₄interface layer. The steps in FIGS. 6B through 6D are then repeated toform a multilayer stack 401 comprising a plurality of reflective layerpairs.

In 6B, while sputtering the silicon target using the RF source andflowing the nitrogen gas in the PVD chamber, the method may furthercomprise co-flowing an inert gas such as argon in the PVD chamber.

In one or more embodiments, the method comprises repeating the steps inFIGS. 6A through 6D to form the multilayer stack 401 comprising 40reflective layer pairs. In some embodiments, the multilayer stackexhibits a reflectivity of 13.5 nm light that is greater than amultilayer stack comprising a plurality of reflective layer pairscomprising silicon and molybdenum that does not include the first Si₃N₄interface layer and the second Si₃N₄ interface layer.

Operation of the RF power source may comprise operating the RF powersource at a frequency in a range of from 5-30 MHz, for example at 13.56MHz. The RF power source may be operated at a power in a range of100-800 Watts (W). Gas pressure during operation of the RF power sourcemay be in a range of 0.5 mTorr to 10 mTorr. When argon and nitrogen areco-flowed, the argon/nitrogen gas flow ratio may be in a range of 0.3 to5. During DC sputtering, the power may be in a range of 300-1500 W, andthe argon gas may be at a pressure in a range of 05.-5 mTorr.

The method may further comprise depositing a ruthenium capping layer onthe multilayer stack. The method may further comprise depositing anabsorber layer on the ruthenium capping layer.

The method to form the multilayer stack may be performed in a PVDchamber as shown in FIG. 2 and a lid as shown in FIG. 3, wherein the PVDchamber comprises a plurality of cathode assemblies including a firstcathode assembly including the silicon target, a second cathode assemblyincluding the molybdenum target, and an upper shield below the pluralityof cathode assemblies including a first shield hole having a diameterand positioned on the upper shield and with respect to the first andsecond cathode assemblies to expose the silicon target during and asecond shield hole having a diameter and positioned on the upper shieldto expose the molybdenum target. In some embodiments of the method, theupper shield has a flat inside surface, except for a region between thefirst shield hole and the second shield hole and a raised area in theregion between the first shield hole and the second shield hole, theraised area having a height sufficient so that during a depositionprocess, the raised area prevents material sputtered from the silicontarget from being deposited on the molybdenum target and to preventmaterial sputtered from the molybdenum target from being deposited onthe silicon target. In some embodiments of the method, the height of theraised area is greater than one centimeter from the flat inside surfaceand having a length greater than the diameter of the first shield holeand the diameter of the second shield hole.

Another embodiment pertains to a method of manufacturing an EUV maskblank comprising forming a reflective layer pair comprising silicon andmolybdenum, wherein forming the reflective layer pair comprises:sputtering a silicon target in a physical vapor deposition (PVD) chamberusing a DC power source and an flowing inert gas in the PVD chamber toform a silicon layer on a substrate; sputtering the silicon target usingan RF power source and flowing nitrogen gas in the PVD chamber to form afirst Si₃N₄ interface layer on the silicon layer and a Si₃N₄ layer onthe silicon target; sputtering a molybdenum target using a DC powersource and flowing an inert gas in the PVD chamber to form a molybdenumlayer on the Si₃N₄ layer; sputtering the silicon target including theSi₃N₄ layer thereon using a DC power source and flowing an inert gas inthe PVD chamber to form a second Si₃N₄ interface layer on the molybdenumlayer until the Si₃N₄ layer is depleted from silicon target and thendepositing a silicon layer on the second Si₃N₄ interface layer;repeating steps (350A) through (350D) to form a multilayer stackcomprising a plurality of reflective layer pairs comprising 40reflective layer pairs; forming a capping layer on the multilayer stack;and forming an absorber layer on the capping layer.

Another aspect of the disclosure pertains to an extreme ultraviolet(EUV) mask blank as shown in FIG. 7. The EUV mask blank comprises asubstrate 400; a multilayer stack 401 which reflects EUV radiation, themultilayer stack comprising a plurality of reflective layer pairincluding a silicon layer 402 and a molybdenum layer 404, and aninterface layer 403 between the silicon layer and the molybdenum layer,the interface layer comprising Si₃N₄; a capping layer 407 on themultilayer stack of reflecting layers; and an absorber layer 409 on thecapping layer. In some embodiments, the multilayer stack comprises 40reflective layer pairs. In some embodiments, the capping layer 407comprises ruthenium. In some embodiments, the absorber layer comprisestantalum. The multilayer stack exhibits, according to some embodiments,a reflectivity of 13.5 nm light that is greater than a multilayer stackcomprising a plurality of reflective layer pairs comprising silicon andmolybdenum that does not include the first Si₃N₄ interface layer and thesecond Si₃N₄ interface layer. In some embodiments, the thickness of eachmultilayer of silicon, interface layer and molybdenum is in a range of5-10 nm, for example 7 nm.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. An extreme ultraviolet (EUV) mask blankcomprising: a substrate; a multilayer stack which reflects EUVradiation, the multilayer stack comprising a plurality of reflectivelayer pairs including a silicon layer and a molybdenum layer, and aninterface layer between the silicon layer and the molybdenum layer, theinterface layer comprising Si₃N₄; a capping layer on the multilayerstack of reflecting layers; and an absorber layer on the capping layer.2. The EUV mask blank of claim 1, wherein the multilayer stack comprises40 reflective layer pairs.
 3. The EUV mask blank of claim 2, wherein thecapping layer comprises ruthenium.
 4. The EUV mask blank of claim 3,wherein the absorber layer comprises tantalum.
 5. The EUV mask blank ofclaim 3, wherein the multilayer stack exhibits a reflectivity of 13.5 nmlight that is greater than a multilayer stack comprising a plurality ofreflective layer pairs comprising silicon and molybdenum that does notinclude the Si₃N₄ interface layer.
 6. The EUV mask blank of claim 1, theinterface layer comprises a first interface layer on the silicon layer.7. The EUV mask blank of claim 6, further comprises a second interfacelayer on the molybdenum layer.
 8. The EUV mask blank of claim 6, whereinthe second interface layer comprises Si₃N₄.
 9. The EUV mask blank ofclaim 8, wherein the multilayer stack comprises 40 reflective layerpairs.
 10. The EUV mask blank of claim 9, wherein the multilayer stackcomprises a first interface layer on every silicon layer and a secondinterface layer on every molybdenum layer that has a silicon layerthereon.
 11. The EUV mask blank of claim 8, wherein each multilayer ofthe silicon layer, the interface layer and the molybdenum layer has athickness in a range of 5-10 nm.
 12. The EUV mask blank of claim 8,wherein the thickness of the multilayer of the silicon layer, theinterface layer and the molybdenum layer is 7 nm.
 13. The EUV mask blankof claim 1, wherein the multilayer stack exhibits a reflectivity of 13.5nm light is greater than a multilayer stack that does not include theinterface layer.